(1) Field of the Invention
A mass spectrometer including an ionization chamber with a feed channel for the gas to be examined, an electron source for ionizing the gas to be examined, electrodes for accelerating the ionizing electrons, electrodes for the mass-dependent separation of the ions by acceleration/deceleration thereof, a detector for the separated ions, and a wiring with metallic wires.
Mass spectrometers are used in many kinds of applications. Whereas mass spectrometers were formerly used primarily for scientific purposes, nowadays there are more and more applications in connection with protection of the environment, measurements of air quality for detecting harmful gases, process monitoring and control, security checks e.g. in airports, and the like. In particular mass spectrometers which have small dimensions and are therefore easy to transport and can be used ubiquitously are suitable for these purposes. For application on a large scale, a further requirement is that these mass spectrometers can be produced cost-effectively.
(2) Description of Related Art
Previously known mass spectrometers having a quadrupole mass separator (WO 2004/013890, GB 2384908 A) are distinguished by small size. The disadvantage is that, in the case of such quadrupole mass separators, very stringent requirements are made of the electrode geometry, with the result that a separator cannot be produced by the etching and deposition methods that are customary in microsystems engineering. Since the systems comprise a plurality of components which have to be aligned and positioned in an accurately fitting manner with respect to one another, expensive and complicated individual system processing is necessary.
In a further mass spectrometer, a magnetic field separator is used (WO 96/16430). However, the latter requires a certain minimum size since, on the one hand, very high magnetic field strengths have to be present for the magnetic field separator, while elsewhere the magnetic field has to be shielded in order not to influence the ionization or ion optics.
In a mass spectrometer produced according to microsystems engineering (YOON H J et al: “Fabrication of a novel micro time-of-flight mass spectrometer”, SENSORS AND ACTUATORS A, ELSEVIER SEQUOIA S. A., LAUSANNE, C H, Vol. 97-98, 1 Apr. 2002 (Apr. 1, 2002), pages 441-447, XP004361634 (ISSN: 0924-4247), the substrate used is silicon, which has the advantage of a great variety of patterning possibilities, but has the disadvantage that large leakage currents that heat the substrate flow. A further disadvantage is the high dielectric constant, which leads to signal corruptions even if an insulating interlayer composed of silicon dioxide is used. Moreover, only a continuous acceleration in the direction of movement takes place, but not a time-variant acceleration perpendicular to the direction of movement of the ions through the electric fields, by means of which the speed-dependent selection of ions can be improved, with the result that all the ions pass to the detector and the measurement of the ion current has to be temporally resolved. In addition, the previously known mass spectrometer is not constructed in complete fashion; separator and detector are separate elements, as is shown in FIG. 11.
A further previously known miniaturized mass spectrometer (WO 96/11492) is likewise not produced in completely planar fashion by the methods of microsystems engineering; external magnets for the mass separation are provided. The corresponding disadvantages have already been mentioned above in connection with another known mass spectrometer (WO 96/16340).
A mass spectrometer of the type mentioned in the introduction was developed for use in a microsystem that can be produced by the customary methods in microsystems engineering (DE 197 20 278 A1). This mass spectrometer has only very small dimensions. However, production is very complex since, on the one hand, said mass spectrometer requires self-supporting insulated grids for the acceleration for the ionization of the gas to be examined and, on the other hand, it is necessary to produce electrically contact-connected, electrolytically grown structures composed of copper and/or nickel. The individual components are constructed separately on a total of four substrates, which have to be connected to form a monolithic system by means of suitable construction and connection technology.